<!doctype html>
<meta charset=utf-8>
<style>
*:nth-child(odd) {
  display: table-header-group;
}
</style>
<script>
document.addEventListener("DOMContentLoaded", () => {
  document.execCommand("enableObjectResizing", false)
  document.addEventListener("selectionchange", () => {
    document.execCommand("insertImage", false, "x")
    document.execCommand("selectAll", false)
  }, { once: true });
  document.getSelection().collapse(a)
})
</script>
<details open="" contenteditable="true">
<details id="a">
